Electrohydraulic valve systems

ABSTRACT

An electrically operated pressure-reducing valve system comprising a moving coil unit mounted for movement within a magnetic field and carrying an obturator and a nozzle carrying fluid at pressure cooperating the obturator so that the movement of the moving coil unit will determine the escape flow of fluid from the nozzle. The nozzle is supplied with fluid at pressure through a restrictor and the junction of the nozzle and the restrictor may supply reduced pressure to a working space for servo adjustment of a servo valve. The moving coil unit includes at least a pair of windings which are connected individually into two electric supply circuits so that the currents in the two circuits may be varied. The variation of the currents in the two circuits may be differential to obtain a desired control effect or alternatively one circuit may be a duplicate of the other circuit and may be switched into operation when the said other circuit fails.

United States Patent [72] Inventor Anthony George Lithgow Shore 2,926,22l 2/ i960 Kagdis I79] 1 I55 wi b b E l d 3,457,956 7/1969 Andrews l37/625.6l pl 1 p 83s6a3 Primary Examiner-Henry T. Klinksiek [22] filed June Attorney-Young 8!. Thompson [45] Patented Aug. 10, I97] [73] Assignee Dowty Technical Developments Limited Broekllannpton, Cheltenham, England [32] Priority June 26, I968 [33] Great Britain l l 30405/68 [54] ELECTROHYDRAULIC VALVE SYSTEMS 2,78l,46l 2/1957 Boothetal. l79lll5.5UX

ABSTRACT: An electrically operated pressure-reducing valve system comprising a moving coil unit mounted for movement within a magnetic field and carrying an obturator. and a nozzle carrying fluid at pressure cooperating the obturator so that the movement of the moving coil unit will determine the escape flow of fluid from the nozzle. The nozzle is supplied with fluid at pressure through a restrictor and the junction of the noule and the restrictor may'supply reduced pressure to a working space for servo adjustment of a servo valve. The moving coil unit includes at least a pair of windings which are connected individually into two electric supply circuits so that the currents in the two circuits may be varied. The variation of the currents in the two circuits may be differential to obtain a desired control effect or alternatively one circuit may be a duplicate of the other circuit and may be switched into operation when the said other circuit fails.

ELECTROHYDRAULIC VALVE SYSTEMS This invention relates to an electrohydraulic or electropneumatic valve system and more particularly it relates to an electrically operated pressure-reducing valve system which may be combined with a servo valve to forman electrohydraulie or electropneumatic servo valve system.

In accordance with the present invention an electrically operated fluid-pressure-reducing valve system comprises a moving coil unit mounted within a magnetic field, a nozzle adapted for connection to a source of fluid at pressure through a fixed restrictor, an obturator mechanically connected to the moving coil to cooperate with the nozzle so as to vary the fluid flow to the nozzle and thus to vary the fluid pressure at the junction between the restrictor and the nozzle in accordance with the clearance between the obturator and the nozzle, a pair of windings forming part of the moving coil unit, and electric supply means having two circuits connected one to one winding and the other to the other winding so that the currents supplied by the circuits induce forces on the coil unit, and means for adjusting the two circuits so that the electric currents in one or the other or both coils may be varied.

The said junction may be connected for fluid pressure operation of a hydraulic or pneumatic servo valve.

In accordance with a further feature of the present invention an electrohydraulic or electropneumatic servo valve system comprises a pair of pressure-reducing valves, each of which includes a moving coil unit having a pair of windings mounted within a magnetic field, a nozzle adapted for connection to a pressure source through a fixed restrictor, and an obturator mechanically connected to the moving coil unit to cooperate with the nozzle so that the pressure of the junction between the restrictor and the nozzle is variable in accordance with the clearance between the nozzle and the obturator, a servo valve adapted to control flow of fluid at pressure to a service in accordance with the control pressures acting on two opposed areas thereof, respective connections from the two junctions to the two control areas, and electric supply means for the moving coil units comprising two circuits one of which includes one winding of each coil unit connected in series and the other of which includes the other'winding of each coil unit connected in series, and means for adjusting the electric currents in one or other or both circuits, the arrangement being such that current flowing in either circuit will tend to produce opposite pressure variations at the two junctions to cause differential force changes to be developed on the control areas.

Where the currents flow simultaneously in the two circuits these currents may be arranged to produce opposing forces within each coil unit.

Alternatively, one circuit may be a duplicate of the other circuit and may be switched into operation when the said other circuit fails.

Various embodiments of the invention will now be particularly described with reference to the accompanying drawings in which,

FIG. 1 is a cross section through an electric hydraulic servo valve incorporating the invention,

FIG. 2 is a diagram illustrating the coil connections with the embodiment of FIG. 1, and

FIGS. 3 and 4 represent alternative circuit diagrams for supplying electric current to the coils. v

The electrohydraulic servo valve shown in FIG. 1 is described in greater detail in Goddardsapplication Ser. No. 835,685. The valve body 1 includes bore 2 within which a spool valve member 3 is slidable. The spool valve member includes three lands 4, 5 and 6 connected by a pair of rods 7 and 8 forming waisted portions. A pair of ports 9 and 11 open into the bore 2 at positions which are continually in connection with the waisted portions occupied by rods 7 and 8. From the ports 9 and 11 hydraulic passages 12 and 13 extend suitably through the valve body I for connection to the service which is to be controlled by the servo valve. A service may for exampie be a conventional double-acting hydraulic ram. Fluid from a source at pressure is supplied into a passage 14 in the body 1 which in turn makes connection with a port 15 opening into the bore 2. The port 15 is so constructed that in the neutral position the spool valve member land 5 just completely closes the port 15, the movement in one direction or the other of the spool will open the pressure port 15 to one or another waisted portion. Also opening into the bore 2 are a pair of return ports 16 and 17 which internally of the body I are connected to a return passage 18. The ports 16 and 17 are normally just closed by the lands 4 and 6 respectively in the neutral position of the spool valve member. The ports l5, l6 and 17 may be provided with metering slots to ensure a desired graduated connection of the ports to the waisted portions on movement of the spool valve in one direction or the other from its neutral position.

Nozzles 19 and 21 extend one from each end of the spool valve member 3 and enter respectively into a pair of diaphragm chambers 22 and 23 which are connected internally of the body to the return passage 18. In the diaphragm chamber 22 a diaphragm 24 is suitably mounted to cooperate with the end of the nozzle 19 so as to vary a restriction to flow of fluid from the central passage 25 within nozzle 19. The diaphragm supports are moving coil 26 within an annular airgap 27 in a permanent magnet structure 28, a strong radial magnetic field acting across the annular gap 27. Within the diaphragm chamber 23 a diaphragm 29 is mounted to cooperate with the end of the nozzle 21 to control the flow of fluid from an. axially extending bore 31 in nozzle 21. Diaphragm 29 also carries a moving coil 32 mounted within an annular gap 33 of a permanent magnet structure 34. The permanent magnet structure 34 provides a strong radial magnetic field across the annular gap 33. Each of the two diaphragms 24 and 25 may be arranged as shown in Daubeney and Shore 5 application Ser. No. 835,684. The valve body 1 may be arranged in accordance with Andrews'application Ser. No. 835,686. Alternatively, the general arrangement of the valve may be as shown in AndrewsU.S. Pat. No. 3,457,956.

The two nozzles 10 and 21 are both of accurately cylindrical shape in that they extend respectively through a pair of bushes 35 and 36 fitted into the ends of the bore 2. The first working space 37 is then provided between the bush 35, the land 4 and the cylinder 2 and the second working space 38 is provided between the bush 36 and the bore 2 and the land 6. Within the block 1 extensions from the pressure passage 14 connect respectively through fixed restrictors 39 and 41 to the two working spaces 37 and 38. Within the working spaces cross bores connect the axial bores 25 and 31 in the nozzle to the working spaces 37 and 38.

It will be appreciated that there are two electrically operated pressure-reducing valves. The first comprises the fixed restrictor 41, the nozzle 21, the diaphragm 29 whichforms the obturator of a nozzle 21 and the moving coil unit 32 carried in the magnetic structure 34 which provides a strong magnetic field across the gap 33. Movement of the diaphragm 29 relative to the nozzle 21 will vary the gap permitted at the nozzle 21 and thus vary the leakage flow of liquid through the passage 31 within the nozzle 21. When the flow varies, the flow through the fixed restrictor 41 will also vary thus varying the pressure drop at restrictor 41. The junction between the restrictor 41 and the nozzle 21 is the working space 38 and within this working space reduced pressure can exert a force on an annular area of the land 6 of spool valve member 3.

The second electrically operated pressure-reducing valve comprises fixed restrictor 39, nozzle 19, diaphragm 24 which forms the obturator for the nozzle 19 and moving coil unit 26 mounted in the magnetic field within gap 27 of magnet structure 28. The working space 37 is the junction of the fixed restrictor 39 and the nozzle 19 and-within this working space the pressure available can act on an annular area of the land 4 of spool valve member 3. This working area is in opposition to the working area in working space 38.

The moving coil unit 32 comprises a former on which a pair of coils A and B are wound, the coils being suitably insulated from one another. The moving coil unit 26 also comprises a former on which two coils C and D are wound, the coils being suitably insulated from one another. Each of the coil units 32 and 26 is preferably arranged as shown in Daubeney and Shore's application Ser. No. 835,684 wherein the spring mounting strips carrying the moving coil unit also form the connections for the coils. Reference is now made to FIG. 2. In coil unit 32 coil A has connections 51 and 52 and coil B has connections 53 and 54. In coil unit 26 coil C has connections 55 and 56 and coil D has connections 57 and 58. Within the whole valve unit electrical connections 59 and 61 connect together respectively connections 51 and 57, and 53 and 55 so that there is a first circuit in between the connections 52 and 58 which includes the coils A and D in series and a second circuit in between the connections 54 and 56 which includes the coils B and C in series.

One method of connection of the coils of the coil units is illustrated in FIG. 3. The output stages of an amplifier are illustrated which comprise two transistors 62 and 63. The bases of these two transistors are supplied with suitable control voltages from a control signal source. The collector of transistor 62 is connected to connection 52 and the emitter of transistor 62 is connected to the positive pole 64 of power source 65. Similarly the collector of transistor 63 is connected to connector 56 and the emitter of transistor 63 is also connected to the positive pole 64. The two connectors 54 and 58 are connected both to the negative pole 66 of power source 65. The applied voltage to the base of the transistor 63 will therefore control the flow of current from positive pole 66 through coils D and A in series. Similarly the control voltage applied to the base of transistor 63 will control flow ofcurrent through coils B and C in series.

The currents flowing through coils A and B from source 65 will produce opposite forces and the difference only of the two forces will react on the diaphragm 29 to cause movement thereof to vary the spacing from the nozzle 21. Similarly the currents flowing through coils C and D produce opposite forces and the difference only will react on the diaphragm 24.

The forces produced on coils A and B for current flow in the one circuit will produce forces which act in the same direction when referred to FIG. 1, i.e. either to the left or to the right. Similarly current flow through coils B and C in the second circuit will produce forces which act either to the left or to the right as shown in FIG. 1. This in turn will mean that the force differences between the coils A and B in unit 32 and coils C and D in unit 26 will also act in the same direction as seen in FIG. I, i.e. either to the left or to the right. Such movement will increase the clearance of the diaphragm from one nozzle and will reduce the clearance of the diaphragm from the other nozzle resulting in increase in pressure in one working space and reduction in pressure in the other working space, i.e. a differential pressure change to urge the spool valve member 3 in one direction.

FIG. 4 shows another method of interconnecting the coils of the coil units. The arrangement shown in FIG. 4 is intended for use where a high degree of safety in operation is required and in this case the two circuits are provided for alternative operation such that if for some reason the current supplying one circuit fails, an automatic switch device switches to the other circuit so that control operation may still be provided. In FIG. 4 the current supplied for the first circuit is fed by an amplifier 67 which connects via connections 52 and 58 to coils A and D. The second circuit is fed by an amplifier 68 which connects through connections 54 and 56 to coils B and C.

Many variations are possible within the scope of the present invention for connecting the four coils A, B, C and D to obtain a desired functional result. For example within the broad scope of the present invention it is possible to connect the four coils A, B, C and D into four completely separate circuits, the resulting movement of the spool valve being effective to sum the controlling currents applied to the four coils. Further it is within the scope of the present invention to provide more than two coils for each moving coil unit in order that further electrical circuits may be applied in the control of one or both moving coil units.

While the described embodiment employs hydraulic operation it is equally within the scope of the present invention to employ pneumatic operation for a mixture of hydraulic and pneumatic operation. For example the two pressure-reducing valves may operate with gas at pressure and may move the main spool 3 to control hydraulic flow to the service. Alternatively the pressure-reducing valves may be hydraulic and may move the main spool valve to control the flow of gas at pressure to the service.

Iclaim:

1. An electrically operated fluid-pressure-reducing valve system comprising, a moving coil unit mounted within a magnetic field, a nozzle adapted for connection to a source offluid at pressure through a fixed restrictor, an obturator mechanically connected to the moving coil unit to cooperate with the nozzle so as to vary the fluid flow from the nozzle and thus to vary the fluid pressure at the junction between the restrictor and the nozzle in accordance with the clearance between the obturator and the nozzle, a pair of windings forming part of the moving coil unit, and electric supply means having two circuits connected one to one winding and the other to the other winding so that the currents supplied by the circuits induce forces on the coil unit, and means for adjusting the two circuits so that the electric current in one or other or both coils may be varied.

2. An electrically operated fluid-pressure-reducing valve system as claimed in claim I wherein the said junction is connected to adjust a fluid pressure or a pneumatic servo valve, moving of the servo valve being arranged to move the nozzle relative to the obturator.

3. An electrohydraulic or an electropneumatic servo valve system comprising, a pair of pressure-reducing valves each of which includes a moving coil unit having a pair of windings mounted within a magnetic field, a nozzle adapted for connec tion to a pressure source through a fixed restrictor, and an obturator mechanically connected to the moving coil unit to cooperate with the nozzle so that the pressure at the junction between the restrictor and the nozzle is variable in accordance with the clearance between the nozzle and the obturator, a servo valve carrying the two nozzles and adapted to control flow of fluid at pressure to a service in accordance with the control pressures acting in two opposed working spaces thereof, connections from the two junctions to the two working spaces, and electric supply means for the moving coil units comprising two circuits, one of which includes one winding of each coil unit connected in series and the other of which includes the other winding of each coil unit connected in series, and means for adjusting the electric currents in one or other or both circuits, the arrangement being such that current flowing in either circuit will tend to produce opposite pressure variations at the twojunctions to cause differential force changes to be developed in the working spaces to move the servo valve, such movement in turn adjusting the nozzles relative to their obturators. 

1. An electrically operated fluid-pressure-reducing valve system comprising, a moving coil unit mounted within a magnetic field, a nozzle adapted for connection to a source of fluid at pressure through a fixed restrictor, an obturator mechanically connected to the moving coil unit to cooperate with the nozzle so as to vary the fluid flow from the nozzle and thus to vary the fluid pressure at the junction between the restrictor and the nozzle in accordance with the clearance between the obturator and the nozzle, a pair of windings forming part of the moving coil unit, and electric supply means having two circuits connected one to one winding and the other to the other winding so that the currents supplied by the circuits induce forces on the coil unit, and means for adjusting the two circuits so that the electric current in one or other or both coils may be varied.
 2. An electrically operated fluid-pressure-reducing valve system as claimed in claim 1 wherein the said junction is connected to adjust a fLuid pressure or a pneumatic servo valve, moving of the servo valve being arranged to move the nozzle relative to the obturator.
 3. An electrohydraulic or an electropneumatic servo valve system comprising, a pair of pressure-reducing valves each of which includes a moving coil unit having a pair of windings mounted within a magnetic field, a nozzle adapted for connection to a pressure source through a fixed restrictor, and an obturator mechanically connected to the moving coil unit to cooperate with the nozzle so that the pressure at the junction between the restrictor and the nozzle is variable in accordance with the clearance between the nozzle and the obturator, a servo valve carrying the two nozzles and adapted to control flow of fluid at pressure to a service in accordance with the control pressures acting in two opposed working spaces thereof, connections from the two junctions to the two working spaces, and electric supply means for the moving coil units comprising two circuits, one of which includes one winding of each coil unit connected in series and the other of which includes the other winding of each coil unit connected in series, and means for adjusting the electric currents in one or other or both circuits, the arrangement being such that current flowing in either circuit will tend to produce opposite pressure variations at the two junctions to cause differential force changes to be developed in the working spaces to move the servo valve, such movement in turn adjusting the nozzles relative to their obturators. 